This invention relates to a composite material having a metal oxide later of a Y123 crystal structure. The present invention is also concerned with a method of preparing such a composite material.
One known method for the preparation of a metal oxide crystal having a Y123 crystal structure includes contacting a seed material with a molten mixture of metal oxides to allow the desired crystal to grow on the seed material. The term "Y123 crystal structure" used in the present specification and claims is intended to refer to a crystal structure similar to that of YBa.sub.2 Cu.sub.3 O.sub.7-x where x is a number of 0-1. The term "Y123 metal oxide" is intended to refer to a metal oxide having a Y123 crystal structure.
As the seed crystal, a magnesia single crystal, a Sm123 metal oxide crystal or a Y123 metal oxide crystal has been hitherto used. The use of a magnesia single crystal has a problem that the crystal which has grown on the magnesia seed crystal forms a Y123 polycrystal rather than a single Y123 crystal. When a Y123 crystal is used as the seed crystal, the molten mixture climbs along the seed crystal so that a holder thereof will be wetted and reacted with the molten mixture.